Sewing machine construction

ABSTRACT

A sewing machine having a mechanism for disengaging the needle bar of the machine from the drive mechanism when the needle carried by the needle bar hits an impenetrable object such as a button, zipper or piece of material. The disengaging mechanism of the preferred embodiment includes an elongated sleeve containing a needle bar tensioned to a fixed axial position within the sleeve by axially aligned spring means and other elements adapted to remain in the axial position under normal operating forces but adapted to permit the needle bar to move axially with respect to the sleeve upon application of abnormal forces when one of the elements is thrown out of normal position. In a modification the disengaging mechanism includes a collar surrounding the needle bar and carrying a spring tension ball bearing adapted to move between a depression in the longitudinal groove in the needle bar. An electrically controlled breaking mechanism disengages the power source of the sewing machine when the needle bar is disengaged in either of the embodiments.

United States Patent 1965 now abandoned. [45] Patented Apr. 13, 1971[54] SEWING MACHINE CONSTRUCTION 5 Claims, 16 Drawing Figs.

[52] US. Cl 112/221 [51] Int.Cl D05b 69/36 [50] Field of Search 112/221[56] References Cited UNITED STATES PATENTS 717,848 l/l903 Hatch l12/221 1,574,184 2/1926 Brigham et al... 112/105 2,218,123 10/1940 Smith112/221X 2,318,200 5/1943 Cobble et al 112/221X FOREIGN PATENTS 938,9462/1956 Germany ABSTRACT: A sewing machine having a mechanism fordisengaging the needle bar of the machine from the drive mechanism whenthe needle carried by the needle bar hits an impenetrable object such asa button, zipper or piece of material. The disengaging mechanism of thepreferred embodiment includes an elongated sleeve containing a needlebar tensioned to a fixed axial position within the sleeve by axiallyaligned spring means and other elements adapted to remain in the axialposition under normal operating forces but adapted to permit the needlebar to move axially with respect to the sleeve upon application ofabnormal forces when one of the elements is thrown out of normalposition. in a modification the disengaging mechanism includes a collarsurrounding the needle bar and carrying a spring tension ball bearingadapted to move between a depression in the longitudinal groove in theneedle bar. An electrically controlled breaking mechanism disengages thepower source of the sewing machine when the needle bar is disengaged ineither of the embodiments.

Patented April 13, 1971 3,575,121

8 Sheets-Sheet l INVENTOR FELIX LBERUBE ATTORNEYS Patented A iril 13,1971 3,575,121

'8 Sheets-Sheet '2 mvgNToR FELIX JBERUB'E Patented April 13, 1971 Y3,575,121

8 Sheets-Shut 4.

INVENTOR FELIX J.BERUBE BY PatentedQApril 13, 1971. 3,575,121

8 Sheets-Sheet 5 WWWM I Pategiied April 13, 1971 3,575,121

8 Sheets-Shoot 6 O Q M/VEA/TOR EW Patented 7 April 13, 1971 8Sheets-Sheet 8 SEWING MACHINE CONSTRUCTION CROSS-REFERENCE TO RELATEDAPPLICATIONS This is a division of US. application Ser. No. 722,522,filed Apr. l, 1968, now US. Pat. No. 3,47l,325, dated Oct. 7, 1969,which in turn was a continuation-in-part of Ser. No. 668,283, filed Aug.30, 1967, now abandoned, which, in turn, was a continuation-in-part ofSer. No. 432,642, tiled Feb. l5, I965, also now abandoned.

BACKGROUND OF THE INVENTION This invention relates to sewing machinesand more particularly to sewing machines of the type employing needlebars.

Sewing machines for industrial and home use may be easily damaged bymalfunctions or misuse of the machine. For

example, in stitching zippers, buckles, snaps, buttons and other metalor hand attachment to a fabric, it is quite possible inadvertently tobring the metal or hard portion of the article into the path of theneedle. In such an event, the needle will usually break or bend. Beforethe machine can be stopped, the broken or bent needle may damage thefabric being stitched or further damage the sewing machine. A broken orbent needle or even a needle which is slightly misaligned can readilystrike the sewing machine plate or some of the mechanism below theplate, necessitating delays and expensive repairs. In addition, such amalfunction may jam the needle which in turn may cause the sewingmachine motor which continues to operate during the jam to burn out. Inaddition, the misuse or malfunctioning of a machine may cause injury tothe operator. Such an injury may occur, for example, when the operatorsfingers are close to the needle at the moment the needle is bent orbroken when it strikes a resistant materialsuch as a zipper or a button.Such problems are particularly acute in high speed industrial machines.

SUMMARY OF THE INVENTION It is an object of the present invention toovercome these and other problems by providing a sewing machineconstruction which is not likely to jam or malfunction when the machineis misused by engaging the pointed end of the needle with a resistantmaterial. It is an object of the present invention to provide animproved sewing machine construction in which needle breakage or damagefor reasons such as set forth above are minimized or substantiallyeliminated. A further object of the present invention is to provide asewing machine construction in which damage to the sewing machine andits component parts including its motor and injury to operators areminimized. Such advantages are attained by providing a construction inwhich the needle bar is automatically disengaged from its drivemechanism if the needle is inadvertently engaged by an impenetrablematerial.

A further object of this invention is to provide a relativelyinexpensive sewing machine construction wherein likelihood of damage tothe sewing machine head and injury to the operator are minimized.

A further object of this invention is to provide a means in which asewing machine needle is automatically operatively disengaged from itsdrive mechanism if the needle hits a foreign impenetrable object, and inwhich the needle is automatically reengaged with the drive mechanismupon removal of the foreign object.

A further object of this invention is to provide a sewing machineconstruction in which the motor drive for the needle bar may beautomatically turned off or disengaged when the needle engages a foreignimpenetrable body.

A further object of this invention is to provide a sewing machineconstruction in which the needle bar may be rotated.

for threading convenience by a needle bar connecting stud.

A further object of this invention is to provide a sewing machineconstruction which is not only relatively inexpensive but is alsorugged, capable of standing considerable abuse, and is easily andinexpensively repaired.

A further object of this invention is to provide a sewing machineconstruction having a needle bar which can be automatically disengagedfrom its drive mechanism in industrial sewing machines operating atextremely high speeds if the needle hits a foreign impenetrable objectwith the needle automatically reengaging with the drive mechanism uponremoval of the foreign object.

In the present invention there is provided a sewing machine constructionhaving a needle bar formed of an elongated shaft with an elongatedgroove extending longitudinally in the shaft. A depression is formed inthe shaft in alignment with the groove and is defined from the groove byan intermediate ridge. A second ridge, if desired, also may be formed inthe shaft and extends in a direction circumferential to the depression.A collar or stud supports and surrounds the needle bar. The collar isreciprocated up and down by a suitable drive means connected to a motordrive source. The motor drive source is provided with an on-off switchwhich may be positioned within the sewing machine head. Means areprovided for interengaging the collar and the needle bar, with thecollar normally interengaged with the depression and adapted toreciprocate the needle bar and needle carried with it when the collar isso normally engaged. Such interengaging means are spring-tensioned orotherwise suitably arranged so that the collar will move from engagementwith the depression to engagement with the elongated groove of theneedle bar when a needle carried by the needle bar meets an unusualamount of resistance. When this occurs the collar rides up and down onthe needle bar with the needle bar thereby operatively disengaged fromthe drive mechanism. When the obstruction is removed the collarautomatically reengaged the depression and the needle and needle bar areautomatically reengaged. Means may be connected to the needle bar forswitching the motor off when the collar moves from a normal position inengagement with the depression. Means are also provided for limitingmovement of the needle bar in one direction so that the collar willautomatically reengage the depression once in each complete cycle ofmovement of the collar when it is in the nonnormal or nonoperatingposition of engaging the elongated slot.

In a preferred form of the invention designed for use in industrialsewing machines an elongated tubular sleeve is supported and secured forvertical movement by a collar which is reciprocated by a suitable drivemeans. The sleeve in turn has its upper end reciprocating in a bushingsecured to the machine. A needle bar positioned at the lower end of thesleeve is axially aligned with a heavy spring and elements that arenormally designed to be positioned axially with respect to the needlebar. On engaging an impenetrable object one of the elements is axiallydisengaged from another to permit relative movement of the needle barand sleeve. A return spring means is provided to return the needle barto its initial position when it disengages from the impenetrable object.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 4 is an enlarged, fragmentarycross-sectional elevation of the needle bar;

FIG. 5 is a cross-sectional view taken along the line 5-5 of FIG. 4;

FIG. 6 is a fragmentary elevation of the needle bar;

FIG. 7 is a cross section taken along the line 7-7 of FIG. 6;

FIG. 8 is a cross section taken along the line 8-8 of FIG. 6;

FIG. 9 is a cross-sectional fragmentary elevation of the sewing machinehead with a needle bar construction of an embodiment designedparticularly for high speed industrial machines shown in a retractedposition;

FIG. 10 is a cross-sectional fragmentary elevational view of the sewingmachine head of FIG. 9 with the needle bar in a down position;

FIG. 11 is a partially cross-sectional elevational enlargement of theneedle bar assembly looking from the right of FIG. 10;

FIG. 11A is a cross-sectional view taken on the line llA-11AofFIG.1l;

FIG. 12 is a cross-sectional elevation of a needle bar assembly of FIG.[1 looking from the left side thereof;

FIG 13 is a cross-sectional elevation of a needle bar assembly embodyinga further modification of the present invention;

FIG. 14 is a cross-sectional fragmentary elevation of a sewing machinehead with a needle bar construction of a preferred embodiment designedparticularly for high speed industrial machines; and

FIG. 15 is a fragmentary cross-sectional elevation on an enlarged scaleof the bar connection shown in FIG. 14.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention isadapted for use with a wide variety of conventional sewing machines.Consequently, the portions of the sewing machines now shown or otherwisedescribed may be conventional in nature. In the embodiment illustrated,the sewing machine casing 1 has a head 2 to which power is supplied fromshaft 3. A lever linkage system 4 interconnects the main drive shaft 3with the needle bar 5. This linkage system 4 includes a lever 6connected to shaft 3 and in turn connected to the pitman 7 through a pin8. The needle bar is supported in upper and lower journals I0 and 11 forvertical movement. Suitable and conventional bushings and locknuts maybe positioned at the upper end of the journal as illustrated at 13 toretain the bushing 10 in position and to help support and limit movementof the needle bar 5. Also positioned within the sewing machine head 2 isan on off switch 14 suitably supported by support within the casing.This switch is connected by wires 16 to the motor (not shown) thatoperates the drive shaft 3. The button 18 of the switch 14 is engaged byand normally controlled by the spring 19 which extends vertically in thecasing head 2 with the upper end of the spring 19 engaging the button18. The upper end of the spring 19 is looped at 20 with one leg of theloop suitably supported on and secured to the switch by a collar and nutarrangement 21. If desired, a light 24 may be supported within thecasing head 2 to illuminate the interior of the head when it is open.This light may be supported on a shaft 25 in turn secured at its upperend to an inwardly extending flange 27 by means of a support means 28.

The needle bar construction is best illustrated in FIGS. 4 to 8. Theneedle bar is formed with a depression 30 in its surface at a point fromthe ends of the needle bar such that a collar 31 carried by the pitman 7will move the needle bar in a normal up and down stroke during operationof the machine.

The depression 30 should have sufficient depth to receive a projectingportion of a ball bearing 32 (FIGS. 4 and 5). The lower wall or ridge 34and a sidewall or ridge 35 that form the depression 30 preferably shouldbe somewhat lower than the curvature of the surface on the bar 5 so asto permit movement of the ball bearing 32 from the depression indirections over the ridges or walls 34 and 35 in a control fwrhion.Longitudinally aligned with depression 30 and extending downwardly fromthe depression a distance of approximately at least one-fourth thelength of the needle bar is an elongated channel or groove 37. Thischannel or groove 37 is fonned in the surface of the needle bar and hasa width sufficient to permit vertical movement of the ball bearing 32 inthe channel or groove 37. A laterally extending groove or channel 38 isalso formed on the surface of the needle bar in lateral alignment withdepression 30. The groove 37 is defined from the depression 30 by theridge 35.

The collar 31 which supports the needle bar is an annular member havinga neck 40 projecting into a collar 41 integral with the lower end of thepitman 7. The collar 31 is formed with a longitudinal opening withinwhich is disposed a spring 44 positioned immediately behind the ballbearing 32. A screw 45 secures the spring within the neck 40 andmaintains the spring in adjustable pressure engagement with the ballbearing 32. Ball bearing 32 is secured within the collar by engagementwith the walls of the needle bar 5. In a normal operative position theball bearing 32 is positioned within the depression 30 as illustrated inFIG. 4. If desired, a screw 48 may be threaded through the collar on theside opposite to the collar 41 for selectively securing the collar 41 tothe needle bar 5 in fixed substantially permanent relationship for anoperation under certain conditions. The screw 48 may be used to securethe elongated leaf spring 51 to the collar. This leaf spring is formedwith offset sections 52 and 53 interconnected by member 54. Lower offsetsection 53 is secured to the collar 31 by the screw 48. The pin 50projects outwardly from the needle bar 5 and is normally positionedimmediately adjacent and in contact with lower offset section 53 of thespring 51. The pin 50, however, may be moved relative to the spring 51into engagement with the interconnecting member 54 as hereinafterdescribed.

The needle bar 5 is provided with a collar 67 positioned below thebottom wall 68. Removably secured to the needle bar below the bottomwall is the grip 70 and a needle 60.

The operation of this invention may be understood from consideration ofFIGS. 1 to 3. FIG. 1 shows the machine in normal operation with theneedle bar in an up position. In this arrangement the ball bearing 32engages the depression 30. On rotation of the drive shaft 3 the needlebar is reciprocated up and down. FIG. 2 shows the normal operation ofthe machine with the needle 60 in its down position. Here again, theball hearing 32 normally engages the depression 30 as it did in the upposition illustrated in FIG. 1. In these positions the spring 51 iscarried by the collar 31 with the pin 50 normally engaging the loweroffset section 53 of the spring 51 and in both of these positions theswitch 14 is not depressed.

When the needle 60 hits an impervious material, such as a metal plate 63or a zipper, the needle 60 and consequently the needle bar 5 arerestrained from normal movement. When this occurs, ball bearing 32 whichserves to key the collar 31 of the driving mechanism to the needle barrides out of the depression 30 and into the elongated slot or channel37. When the ball bearing 32 is in the slot 37 the needle bar 5 and theneedle 60 remain substantially motionless and in engagement with theimpervious material 63. The downward movement of the collar 31 causes arelative movement of the spring 51 to the pin 50. This, in turn, causesthe spring 51 to move away from the needle bar 5 as the pin 50 passesover the interconnecting portion 54. This movement of the spring 51presses the spring 19 which in turn presses the button 18 of the switchM and causes the motor driving the shaft 3 to turn off. The operator maythe remove the impervious material 63. After this is done the driveshaft 3 may be turned by hand until the collar 31 recycles to itsuppermost position. When it recycles to its uppermost position thecollar 31 will move out of the elongated groove 37 and into thedepression 30, thereby automatically resetting and retiming variouscomponents so that they assume the positions illustrated in FIG. 1. Theneedle bar 5 which may move with the collar 31 due to the frictionbetween the ball bearing 32 and the sides of the groove 37 is limited inits upward movement by engagement of the collar 67 with the bottom 68 ofthe casing head.

The machine may operat without a switching mechanism, such as shown at18, 19, 14. In such an arrangement the drive will continue to operateuntil the operator stops the machine.

But, while it is operating the ball bearing 32 will move in and out ofthe depression 30 once each complete cycle of the drive shaft 3. Whenthis occurs, the needle bar 5 will be disengaged on each downwardmovement of the collar 31 and reengaged upon each upward movement of thecollar 31. Thus the needle bar and the needle 60 will have nosignificant downward force while the impervious material 63 is stillobstructing the normal movement of the needle 60.

The lateral groove 30 may be used for ease in rethreading the needle 60.Quite often it is easier for the operator to thread the needle 60 if theneedle can be turned at right angles. By utilizing a needle bar such asillustrated, the operator may rotate the needle 60 by turning the grip7090. This, in turn, will cause the ball bearing 32 to move from thedepression 30 into the lateral groove 38 thereby rotating the needle 6090 so that the eye in the needle faces the operator. Thus as groove 30is laterally aligned with the depression 30, the operator may readilyreturn the needle bar to its normal position by reengaging the ballbearing 32 with the depression 30.

Referring now to FIGS. 9 to 11 inclusive, there is illustrated anembodiment of the invention designed especially for use with high speedindustrial sewing machines in which the very high speeds of operationrequire use of a mechanism in which the effects of inertia areminimized. In this embodiment the sewing machine casing 1, head 2, shaft3 and lever linkage system 4 may all be similar to the arrangementpreviously described. Similarly the on-off switch 14, support 15, wires16, button 10, spring 19, loop 20, collar nut arrangement 21, light 2 1,shaft 25, inwardly extending flange 27 and support means may be similarin construction to and may be used for purposes similar to thecorrespondingly numbered elements previously described. in thisembodiment the spring 19 may be modified as desired so as to properly beengaged by the actuating mechanism of the needle bar hereafterdescribed.

In this modification the needle bar construction generally illustratedat 100 includes includes an elongated sleeve 101 which is secured to thedriving mechanism by collar 31, similar to collar 31 of the previouslydescribed embodiment. The tubular sleeve 101 is adapted to be movedaxially by the collar 31 with the upper end of the sleeve 101 guided forvertical movement by the bushing 102. Thisbushing 102 is in turnthreadingly engaged in the upper end of the casing 1 and may be providedwith external threads adapted to permit vertical adjustment of thisbushing. Preferably this bushing 102 is provided with a horizontal loweredge 103. A needle bar 104 having a conventional lower end is positionedwith is upper end extending into the sleeve 101. This needle bar 104 hasa portion 105 that acts as a bearing surface in engagement with theinner surface of the sleeve. The upper end of the needle bar has asection 106 that is flattened or removed to provide a longitudinal space107. The section 106 in addition to being flattening along onelongitudinally extending segment is also of smaller cross-sectionaldiameter than the lower portion of the needle bar so as to permit theencirclement of this segment 106 by an elongated helical fine spring100. This spring 100 engages the shoulder 100 formed between the lowerportion of the needle bar 104 and the segment 106. The upper end of thefine spring 100 engages a flange 110 that is integrally formed with thesegment 106 with the outer periphery of the flange 110 acting in bearingengagement with the inner surface of the sleeve 101. A pin 111 extendsacross and through the sleeve 101 with the pin 111 positioned in thespace 107 and adapted to engage the flattened surface segment of theneedle bar to prevent the needle bar from inadvertently rotating. Thispin 111 also engages the flange 110 and prevents removal of the needlebar 101 from the sleeve 101. This pin 111 also engages the fine spring108 at its upper end and is adapted to compress this spring therebyexerting downward tension on the needle bar, in the event the needle baris moved upwardly relative to the sleeve 101. Extending upwardly fromthe flange 110 and preferably integrally formed with the needle bar 104,is a vertically extending pin 112. This vertically extending pin 112 isadapted to extend freely through a coaxial hole in the plug 113. Plug113 is free to move within the sleeve 101. The lower end of plug 113 issupported in spaced relation from the flange by a relatively heavyspring 114 with respect to the light spring 100. The spring 114 has alower end that engages the upper surface of the flange 110 and an upperend that engages the lower surface of plug 113 with this spring 114coaxial with pin 112. The upper end of the vertical pin 112 is coplanarwith the upper end of the plug 113 under normal conditions with thesecoplanar ends normally adapted to engage the lower end 115 and thelocking arm 116. This locking arm 116 is pivotally secured at is upperend 117 to a plug 110 with the plug 118 normally flxed within the upperend of the sleeve 101. The plug 110 is fixed within the sleeve by meansof a horizontally extending setscrew 119 that extends horizontallythrough the plug 110 and is adapted to be tightened against the innersurface of sleeve 101. This setscrew 119 is thus used for minor verticaladjustments of the plug. The setscrew 119 may be adjusted through anenlarged hole 120 in the upper end of sleeve 101. A setscrew 121 closesthe upper end of the sleeve 101 and secures the plug 119 againstmovement from within the sleeve 101.

The locking arm 116 is adapted to pivot from a position extendinglongitudinally within the sleeve 101 in which the lower end 115 of thelocking arm is in' engagement with the upper surface of the plug 113with the boss engaging groove 131, to a position in which the lockingarm 116 has pivoted through a slot 122 in the sleeve 101 so that thelower end 115 of the locking arm is disengaged from the plug 113. Theoutward pivoting of this locking arm, as illustrated in FIG. 11, islimited by engagement of the locking arm with the lower edge 103 of thebushing 102.

ln the operation of this device, the needle bar is disengaged from thedriving mechanism when the needle carried by the needle bar hits aforeign, impenetrable object. Under these circumstances, the needle baris restrained against downward movement as the sleeve 101 movesdownwardly. This downward movement of sleeve 101 carries the plug 119downwardly thereby forcing the lower end 115 of the locking arm 116downwardly with increased force against the plug 113. This causes theplug 113 to move downwardly against the force of the heavy spring 114.ln turn, the upper surface of the plug 113 is moved downwardly below theupper surface of pin 112 thus causing the smaller pin 112 to exert asignificant force against the arcuate surface 115 of the locking arm116. This localized force on the arcuate surface 115 causes the pin 112to disengage boss 130 and slot 131 and kick the locking arm out of theslot 122 thereby allowing the sleeve 101 to reciprocate freely andindependently of movement of needle bar 104 as the drive mechanism isstill operating. The upward movement of sleeve 101 on the return cycleafter the obstruction has been removed, causes the lower edge of bushing102 to force the arm 116 back to its original position. At the same timethe upper surface of pin 112 is retracted to the level of the uppersurface of plug 113 when the pin 110 carried by the sleeve 101 hascompressed spring 108 thereby causing the upper end of pin 112 to beretracted within plug 113. Thus, the return of the locking arm 116 isnot blocked by 1 the upper end of pin 112. A master on-off control maybe actuated by a spring 19A as desired by the operator. In the event theon-off control is made operative, it will function in the same fashionas previously described in connection with switch 14 of FIG. 1.

Referring now to the embodiment illustrated in FlG. 13, there is shown aneedle bar 200 of conventional design which in turn may be engaged by acollar 31 of the type previously described. This needle bar 200 isprovided with a suitable key to prevent rotation of the needle barwithin the sleeve 201. The upper end of this needle bar 200 is engagedby a helical spring 202 that extends longitudinally within the sleeve201. The upper end of this spring 202 is engaged by a setscrew 203 thatis threaded downwardly into the upper end of the sleeve 201. Thus, inthis arrangement, the particular adjustment of the setscrew 203 may beused to provide a tension on the upper end of the needle bar 200 forcingit downwardly against restraint of pin 205 which also functions as theabovementioned key extends through an elongated vertical slot 206 in theneedle bar 200. Pin 205 is anchored in sleeve 201 and as illustrated atthe upper limit of slot 206. When a needle carried by the needle bar 200is restrained by an impenetrable object, it permits relative movement ofsleeve 201 and bar 200 with the degree of movement being determined bythe relative adjustment of the setserew 203 and the strength of thespring 202.

There is illustrated in F105. 14 and 15 an embodiment which isparticularly useful and intended for extremely high speed industrialmachines. This embodiment is designed to operate on industrial sewingmachines that have speeds in the order of 4,500 rpm. or more. Themodifications previously discussed are not intended for continuousoperations in sewing machines that operate at these relatively highspeeds. The construction shown in FIGS. 14 and 15 is an integral unitcapable of being easily and quickly installed without special equipmentor training by a sewing machine operator.

In this arrangement the needle bar 300 is provided with an end 301adapted to have a conventional sewing needle secured to it in aconventional fashion. The other end 302 of the needle bar extends into asupport means generally illustrated at 303. The embodiment illustratedin this support means comprises generally an elongated sleeve with theneedle bar 300 having its end 302 extending into it. Support member 303is secured to drive member 310 of the sewing machine by a collar 311having suitable keying means for rigidly interengaging the collar 311 tothe member 303. Thus on operation of the drive mechanism 310 and therotation of the arm 312 the member 303 will oscillate in directionslongitudinal of its axis, thereby effecting an up and down motion of theneedle 314 carried by the needle bar 300.

The needle bar 300 is keyed against rotation by means generallyillustrated at 304. This means preferably comprises a slot 305 in theneedle bar 300. A pin 306 extends across the slot with the ends of thepin 306 secured in the sleeve 303.

Means are provided for securing the needle bar 300 against longitudinalmovement relative to the sleeve 303. This means is generally illustratedat 316 and consists primarily of a pair of elements 317 and 318. Element317 consists of a frustoconic element having an annular end 315 taperingto a bottom end 319 which preferably is closed except for an axiallyextending opening. The member 317 is formed with a longitudinal slot 320that effectively permits the member 317 to function as a spring in adirection normal to its length and as a fixed element in a directionparallel to its length. The element 317 normally interengages theelement 318. Element 318 consists of an inner tube which has a beveledend or shoulder 324 adapted to engage the end 315 of the member 317. Theouter radius of the member 317 at end is less than the outer radius ofthe end 324 of tubular element 318 but greater than its inner radius.The normal positions of the ends 32 1 and 315 are in longitudinalbutting alignment, as illustrated in H6. 15. The element 317 engages therelatively heavy spring 330 at its end 319. The other end of the helicalspring 330 butts and bears against the end 302 of the needle bar 300.Spring 330 has sufficient strength to normally retain the end 302 of theneedle bar 300 and the end 319 of the element 317 in fixed relativelocations during the dynamic state of the needle bar and also tomaintain ends 315 and 324 in longitudinal engagement. However, when animpenetrable object is encountered during the operation of the sewingmachine and by the needle 314, the spring 330 will compress.

A pin 331 extends through the opening in bottom 319. One end engages end302 of the needle bar 300. The other end of the pin 331 engages in fixedor separable relation the stop 333. The stop 333 fits into the element313 near its end 324 and is adapted to be retained in this positionunder normal and d namic operating conditions by helical spring 334.Sprin 334 is a helical spring extending lengthwise within elemen 318 andhaving less power than spring 330. One end of this spring 334 engagesstop 336 while the other end of the spring 334 engages and is preferablysecured to the boss 338 of the stop 333. Stop 336 closes the end ofelement or tube 318. This stop is secured in the tube 318 by a pin 341which extends across or through the stop 336 and has its endsterminating within the tube 318. The stop 336 has an enlarged head 343which forms a screw with this head having an externally threaded surfaceengaging threads on the inner surface of sleeve 316.

The stop 333 has an enlarged flange or lip 350 having an outer surfacethat substantially engages the inner surface 353 of the element 317.Under normal operating conditions surfaces 350 and 353 are in facingengaging relation with one another. Under these conditions the outerperiphery of element 317 at end 315 is always in engagement with the end324 of the element 318. However when the needle 314 hits a relativelyimpenetrable object the needle bar 300 is forced longitudinally in thedirection of arrow 360 against the resistance of spring 330. If there issufficient force applied, spring 330 is compressed between end 319 and302. This causes relative movement of the pin 331 with respect toelement 317 and in turn causes the stop 333 to move longitudinallywithin inner tube 318 in the direction of arrow 360 against theresistance of the relatively light spring 334. When the stop 333 movesinto the tube 318 the end 315 of the member 317 compresses radially andas it does it will move into the end 324 of the member 318, thuspermitting the needle bar 300 to move in the direction of arrow 360relative to the casing sleeve 316. When the impenetrable object isremoved the tension of spring 330 will cause the needle bar 300 to movelongitudinally once again relative to the sleeve 316 in a directionopposite to arrow 360. This in turn is coupled with the expansive forceof spring 334 which forces the stop 333 and element 317 from within thetube 318, thereby returning the unit to its original relative positionbefore needle 314 hits an impenetrable object.

lclaim: 1. ln a sewing machine construction, a needle bar, a needlecarried by said needle bar, a sleeve within which said needle bar maymove in an axial direction;

means for vertically reciprocating said sleeve; disengageable means forinterlocking said needle bar and sleeve, said disengageable meansincluding a locking arm, means pivotally securing said arm to saidsleeve, and means secured to said needle bar engaging said arm undernormal dynamic operating conditions and disengaging from said arm whensaid needle bar is restrained directly and in response to engagement ofsaid needle with an an impenetrable object during axial advancement ofsaid needle bar toward said impenetrable object. 2. A device as setforth in claim 1 wherein said means pivotally securing said arm includesa plug coaxial with and within said sleeve,

means positioning said plug in normal spaced relation to the end of saidneedle bar and in engagement with said arm;

means secured to said needle bar adapted to move relative to said pluginto engagement with said arm to pivot it from engagement with saidplug.

3. A device as set forth in claim 2 wherein said means secured to saidneedle bar includes a pin coaxial with and extending from one end ofsaid bar through into a hole in and coaxial with said plug.

4. A device as set forth in claim 3 including a pair of springs with onespring positioned between said plug and said needle bar and coaxial withsaid pin, and the other spring coextensive with a portion of said needlebar and engaging said needle bar.

5. A device as set forth in claim 4 including a pin extending acrosssaid sleeve and engaging said other spring, said other spring beingfiner than said first-mentioned spring.

1. In a sewing machine construction, a needle bar, a needle carried bysaid needle bar, a sleeve within which said needle bar may move in anaxial direction; means for vertically reciprocating said sleeve;disengageable means for interlocking said needle bar and sleeve, saiddisengageable means including a locking arm, means pivotally securingsaid arm to said sleeve, and means secured to said needle bar engagingsaid arm under normal dynamic operating conditions and disengaging fromsaid arm when said needle bar is restrained directly and in response toengagement of said needle with an an impenetrable object during axialadvancement of said needle bar toward said impenetrable object.
 2. Adevice as set forth in claim 1 wherein said means pivotally securingsaid arm includes a plug coaxial with and within said sleeve, meanspositioning said plug in normal spaced relation to the end of saidneedle bar and in engagement with said arm; means secured to said needlebar adapted to move relative to said plug into engagement with said armto pivot it from engagement with said plug.
 3. A device as set forth inclaim 2 wherein said means secured to said needle bar includes a pincoaxial with and extending from one end of said bar through into a holein and coaxial with said plug.
 4. A device as set forth in claim 3including a pair of springs with one spring positioned between said plugand said needle bar and coaxial with said pin, and the other springcoextensive with a portion of said needle bar and engaging said needlebar.
 5. A device as set forth in claim 4 including a pin extendingacross said sleeve and engaging said other spring, said other springbeing finer than said first-mentioned spring.